There is a need, in the field of graphic arts, for an image forming system which exhibits high contrast photographic characteristics to provide for the good reproduction of continuous tone images by means of a dot image and the good reproduction of line images.
Special developers, known as lith developers, have been used conventionally for this purpose. Lith developers contain hydroquinone as the developing agent and the sulfite which is used as a preservative is used in the form of an adduct with formaldehyde so as not to inhibit the infrectious development. The free sulfite ion concentration is maintained at a very low level. Consequently, the lith developers are very susceptible to aerial oxidation and suffer from a major disadvantage in that they cannot be stored for more than 3 days.
The methods in which hydrazine derivatives are used which have been disclosed in U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,211,857 and 4,243,739 are methods in which high contrast photographic characteristics are achieved using a stable developer. Photographic characteristics of high speed and high contrast can be obtained with these methods, and it is also possible to add high concentrations of sulfite to the developer and so the stability of the developer with respect to aerial oxidation is very much greater than that of a lith developer.
However, when ultra-high contrast images are formed using these hydrazine compounds there is a problem with developer deterioration, in that the density falls and the gradation becomes softer as a result of changes in pH due to aerial oxidation of the developer, loss of developing agent and the accumulation of inhibitors.
More precisely, in high contrast developers which contain hydrazine compounds, D.sub.max is liable to change with variations in pH, and when used over long periods of time with high processed volume bromides and inhibitors accumulate during the processing of the sensitive material, development is inhibited by the effect of the materials which have dissolved out during processing, and this leads to a lowering of D.sub.max.
As a result of various investigations aimed at countering these problems, accelerating agents such as the amino compounds disclosed in JP-A-60-140340 (the term "JP-A" as used herein signifies "unexamined published Japanese patent application"), the phosphonium salt compounds disclosed in JP-A-61-167939, the disulfide compounds disclosed in JP-A-61-198147, and the amino compounds which have an adsorbing group disclosed in JP-A-57-129434, Japanese Patent Application Nos. 61-271113 and 61-280998, have been added in an attempt to lessen the problem of the fall in D.sub.max by raising the value of D.sub.max in the early stages However, it has not been pOSsible tO prevent the fall in D.sub.max due to the passage of time or long term usage. Furthermore, problems exist with the formation of spots of developed silver known as black spotting (black pepper)